The use of an array of print heads in ink-jet printing is well known in the art as disclosed in the above-noted pending parent application Ser. No. 11/773,549. Briefly, ink-jet printing comprises ejecting ink droplets from orifices in a print head onto some type of receiving media to form a desired image. Generally, this formed image comprises a grid-like pattern of drop locations usually referred to as pixels. Often, the image resolution is indicated by the number of ink drops or dots per inch (dpi) commonly having a resolution of from about 300 dpi to about 600 dpi. The disclosure of parent application Ser. No. 11/773,549 details this ink jet process precisely and is totally incorporated by reference into the present disclosure.
U.S. Pat. No. 5,389,958, assigned to the assignee of the present application, is an example of an indirect or offset printing architecture that utilizes phase change ink. The ink is applied to an intermediate transfer surface in molten form having been melted from its solid form. The ink image solidifies on the liquid intermediate transfer surface by cooling to a malleable solid intermediate state as the drum continues to rotate. When the imaging has been completed, a transfer roller is moved into contact with the drum to form a pressurized transfer nip between the roller and the curved surface of the intermediate transfer surface/drum. A final receiving web such as a sheet of media is then fed into the transfer nip and the ink image is transferred to the final receiving web.
Inks usable in the present invention are like those described in U.S. Pat. No. 5,389,958 and U.S. Pat. No. 4,889,560. The disclosures of U.S. Pat. No. 5,389,950 and U.S. Pat. No. 4,889,560 are also incorporated by reference into the present disclosure. U.S. Pat. No. 5,389,958 indicates “the ink used to form the ink image preferably must have suitable specific properties for viscosity. Initially, the viscosity of the molten ink must be matched to the requirements of the ink jet device utilized to apply it to the intermediate transfer surface and optimized relative to other physical and rheological properties of the ink as a solid, such as yield strength, hardness, elastic modulus, loss modulus, ratio of the loss modulus to the elastic modulus, and ductility. The viscosity of the phase change ink carrier composition has been measured on a Ferranti-Shirley Cone Plate Viscometer with a large cone. At about 140° C. (older version of ink, the current is 120 C) a preferred viscosity of the phase change ink carrier composition is from about 5 to about 30 centipoise, more preferably from about 10 to about 20 centipoise and most preferably from about 11 to 15 centipoise. The surface tension of suitable inks is between about 23 and about 50 dynes/centimeter. An appropriate ink composition is that described in U.S. Pat. No. 4,889,560 issued Dec. 26, 1989 and assigned to the assignee of the present invention.
Such an ink has a composition comprising a fatty amide-containing material employed as a phase change ink carrier composition and a compatible colorant. The fatty amide-containing material comprises a tetraamide compound and a monoamide compound. The phase change ink carrier composition is in a solid phase at ambient temperature and in a liquid phase at elevated operating temperature. The phase change ink carrier composition can comprise from about 10 to about 50 weight percent of a tetraamine compound, from about 30 to about 80 weight percent of a secondary monoamide compound, from about 0 to about 40 weight percent of a tackifier, from about 0 to about 25 weight percent of a plasticizer, and from about 0 to about 10 weight percent of a viscosity modifying agent.”
As noted in the above referenced prior art patents, the usable ink also used in the present invention is in a solid phase at ambient temperature and in a liquid phase at elevated operating temperatures.
High speed direct ink-jet marking is enabled by arranging modular print heads in staggered arrays to cover the process width. The architectures for these marking engines typically have many heads to provide the needed speed and resolution. The 6-color fixture uses a plurality of solid ink print heads. In previous ‘print on drum’ printer configurations, the head purge will force the ink to flow from the orifices and run down the print face into a drip bib which directs the flow between the heads and drops in a waste tray. In a direct to paper implementation, the plane of the head is 0.8 mm from the paper thus the drip bib sheet metal which extends beyond the head face will tear the paper. Thus a new style drip bib is required which is flat and does not break the plane of the head and hit the web. The print heads are arranged so that any free dripping ink from the drip bib will not land on the top of a head. Unfortunately, the free ink will land on paper below the head. In the present invention, to stop the ink from dripping, it would be helpful to freeze the ink between the heads so that the ink can be released when a maintenance cycle is performed. When a drip tray is placed below the drip bib, it can be heated to release the drip into a tray.